The present invention relates to an apparatus and a fabrication method of a semiconductor light emitting element using a metal substrate, and more particularly relates to an apparatus and a fabrication method of a semiconductor light emitting element that can include forming a metal substrate on a nitride semiconductor.
A nitride semiconductor device is capable of emitting a high-power, short-wavelength light, and can be widely used as a white light LED (Light Emitting Diode) that combines, for example, a blue or green LED and a fluorescent material. In addition, the nitride semiconductor device has been actively studied in recent years for use as a high-speed electronic device such as a HEMT (High Electron Mobility Transistor).
A nitride semiconductor device can be fabricated by homoepitaxially growing a nitride semiconductor layer on a gallium nitride (GaN) substrate that is identical to the semiconductor to be grown. However, a GaN substrate is expensive. Therefore, in general, a nitride semiconductor device is usually fabricated by heteroepitally growing the nitride semiconductor layer on a substrate (growth substrate) such as sapphire that is different from the semiconductor to be grown.
Since sapphire is an insulator, it is difficult to fabricate a vertical semiconductor device on sapphire. In addition, since sapphire has a low thermal conductivity, it is difficult to fabricate a semiconductor device where a large current flows.
A nitride semiconductor device can be formed on a conductive substrate on a nitride semiconductor layer (See Japanese Patent Application Publication No. 2001-244503). The nitride semiconductor device described in Japanese Patent Application Publication No. 2001-244503 is fabricated as follows. A conductive substrate that is a hetero-substrate is grown on a nitride semiconductor layer which was heteroepitaxially grown on a sapphire substrate during a wafer process for fabricating a plurality of devices at one time. The nitride semiconductor layer is transferred to the conductive substrate by peeling off the sapphire substrate and is diced into an individual chip.
In addition, a nitride semiconductor device can be formed on a plated metal substrate, which is conductive and has a high thermal conductivity, on a nitride semiconductor instead of using a metal plate (See, for example, Japanese Patent Application Publication No. 2007-142368, Japanese Patent Application Publication No. 2007-081312, and Japanese Patent Application Publication No. 2007-088048). For example, the fabrication method of the nitride semiconductor device described in Japanese Patent Application Publication No. 2007-081312 is as follows. When a plurality of devices are fabricated, a nitride semiconductor layer is separated in advance by forming grooves on a growth substrate corresponding to each of the devices to be fabricated. The grooves of the nitride semiconductor layer are filled with a sacrificial layer and a plating substrate is formed on a p-type semiconductor layer as well as the sacrificial layer by plating. After the growth substrate is peeled off, the sacrificial layer is removed and the plating substrate is divided into devices.
When a support substrate is formed by metal plating using, for example, the fabrication method described in Japanese Patent Application Publication No. 2001-244503, there are various problems since the plating layer is thinner than a metal plate. For example, after the growth substrate is peeled off, if the nitride semiconductor layer and the plating substrate are warped due to warpage distortion by a stress of the metal plating, wafer processes become difficult to conduct. In addition, for example, dicing of the metal plating becomes difficult. Furthermore, if the support substrate is formed for each individual separate device by metal plating in order to avoid the problems in the wafer process, the mass-productivity becomes poor.
For example, according to the technology described in Japanese Patent Application Publication No. 2007-081312, effects of warpage of the semiconductor layer after the growth substrate is peeled off can be reduced by forming grooves on the growth substrate and separating the nitride semiconductor layer in advance so as to correspond to each of the devices. However, the fabrication process becomes complex since a filling process for filling the grooves with a sacrificial layer and a process for removing the sacrificial layer after the filling process are required.